1. Field of the Invention
The present invention relates to grinding machines having a grinding finishes onto wheel for grinding metallic workpieces with a high degree of accuracy, and, more particularly, to a method of and apparatus for controlling grinding machines.
2. Description of the Prior Art
As is well-known, a grinding machine comprises a bed or base, a column vertically fixed to the bed, a grinding wheel carried by the column, a cross table horizontally movably mounted on the bed and a slide table which is horizontally movably mounted on the cross table to hold a workpiece to be ground. The grinding wheel is rotatably and vertically movably carried by the column in such a manner as to be brought into grinding contact with the workpiece held on the slide table. Specifically, the cross table is so mounted on the bed as to move forward and rearward and the slide table is so mounted on the cross table as to move rightward and leftward so that they may feed the workpiece into the grinding wheel during grinding operations. Of course, the horizontal movements of the cross table and the slide table are adjusted according to the width and length by which the workpiece is to be ground, and the vertical movement of the grinding wheel is controlled according to the grinding allowance or depth by which the workpiece is to be ground. Also, since the grinding wheel is severely worn during grinding operations, it is necessary to dress the grinding wheel on occasion to continue accurate grinding operations.
As to the grinding machine, grinding conditions vary in material and hardness of workpieces to be ground, length, width and depth to be ground from workpieces and hardness, width and peripheral speed of the grinding wheel. Therefore, it has been very difficult to control the rotation and the vertical movement of the grinding wheel and the horizontal movements of the cross table and the slide table. Also, it has been impossible to automatically control with a high degree of accuracy the grinding machine since not only do the grinding conditions vary, but the grinding wheel will also be severely worn.